@Jon14....... Hi there Jon, I am assuming it is not something simple like you have changed your listing to another, in which case your 2 other reviews would stay with your previous listing!! Your listing definitely only shows one review.....
I am not aware that there is an expiry date on reviews but, over the past few days there have been a number of posts from hosts who are seeing their reviews (mine included) in a different order to that which has traditionally been used. It appears that since Airbnb changed their dashboard format a couple of months ago some of these 'glitches' seem to be creeping into the system.
You would possibly be best advised to get onto Airbnb on....United States and Canada. +1-415-800-5959 / +1-855-424-7262 (toll-free) or through their social media pages... (Twitter being the fastest) and state your issue.
It will be very difficult to actually get any pertinent information out of Airbnb, but their staff are good at rectifying maintenance issues with individual pages. If it's a policy thing, forget it, you will be 'stonewalled' but, if it's a fixable error they should be able to restore these reviews for you. Hope this help Jon....cheers.....Rob